The present invention relates to a plastic bag for containing produce or other food products and which includes an improved valve structure which permits the bag to be vented without permitting atmospheric air to enter the bag or which also includes a wall structure which permits atmospheric air to enter the bag at a controlled rate to maintain product freshness.
By way of background, certain green leafy vegetables, such as cabbage and lettuce, are frequently shredded and placed in polyethylene bags for sale. There are enzymes in such produce which use oxygen within the bag and give off carbon dioxide which bloats the bag. In the past, holes have been placed in the bag walls to let out the carbon dioxide. However, this admits atmospheric air with unlimited amounts of oxygen which causes browning of the cut surfaces of the vegetables due to excessive oxidation, and thus the produce will tend to decay and lose its flavor and give off odors. Thus, two objectionable situations existed. If the bag did not have holes in it, it would bloat and become unsightly. If it did have holes in it, the produce would spoil. In addition, with the event of microwaving, products which may not necessarily bloat the bag during storage, are sold in plastic bags for microwaving purposes. However, such bags, if not suitably vented, would be bloated and rupture during microwaving because of the generation of gases.